Hydraulic fracturing is a process whereby fluid under pressure is used to fracture open the shale, such as that in the Marcellus Shale, to greatly enhance the recovery of natural gas or oil. The fluid used in hydraulic fracturing (often referred to as “fracture water,” “frac water” or “frac fluid”) is primarily water. Other components of frac fluid may include proppant, hydrochloric acid, glutaraldehyde as a biocide, sodium chloride, ethylene glycol and various components for scale inhibitor and iron control. The exact composition of frac fluid may vary.
Disposal of frac fluid that is returned from a well (flowback) is one of the biggest challenges facing the recovery of natural gas from shale. Each well can produce millions of gallons of flowback water because after the fracturing process a large percentage of the water used is pumped back up the well in order to produce the natural gas. Ground water can be protected by properly casing the well, but the problem lies in the safe disposal of the flowback water which can contain arsenic, manganese, cobalt, chromium, lead, various other metals and organic substances, as well as compounds added by the manufacturer.
Current disposal systems are unsatisfactory for environmental or economic reasons and do not always provide for the recycling of frac fluid. These disposal methods include deep well injection, or trucking the waste to industrial or municipal water treatment facilities.
This disclosure describes a novel system for treating a fluid, such as industrial wastewater or frac flowback fluid that is contaminated with heavy metals.